Air filter for an internal combustion engine

ABSTRACT

An air filter for an internal combustion engine having a housing ( 10 ) and a filter element ( 11 ) which is arranged in the housing. The housing ( 10 ) is provided with a filtered air outlet ( 15 ) and at least one untreated air inlet ( 16 ) with a screen ( 17 ) or a closable flap. An auxiliary untreated air inlet ( 18 ) which is closed by a flap valve ( 19 ) is also provided. The screen ( 17 ) or the flap of the untreated air inlet ( 16 ) opens when the temperature of the untreated air is above a certain threshold value and closes when the temperature of the untreated air is below a certain threshold value.

BACKGROUND OF THE INVENTION

The invention relates to an air filter for an internal combustionengine.

In internal combustion engines for motor vehicles the raw air inlet isusually arranged in an area into which cold air can enter unhampered.The air inlet is therefore normally situated behind the radiator grilleof the vehicle or in the area of a fender. It has been found that, inespecially cold countries, when travel is encumbered by heavy snowfalland swirling snow, snow is drawn in with the raw air, and this snow isdeposited on the filter insert and, under certain circumstances, clogsthe filter insert. This causes the motor to stall.

It is furthermore disadvantageous that, when the motor is turned off,the snow on the air filter insert thaws and forms an ice coating whichprevents the entry of air into the motor and thus interferes with thestarting of the motor.

It is therefore proposed in G 93 07 147.7 to provide an air filter foran internal combustion engine in which the raw air inlet is providedwith a sieve. Furthermore, a second raw air inlet is provided, which hasa flap valve, this valve opening depending on the vacuum prevailing inthe filter housing. This signifies that the penetration of snow ishampered by the sieve and —in case the sieve is plugged with snow—thesecond flap opens and thus snow-free raw air can be drawn in. The sievethus effectively prevents the penetration of snow. Of course, this hasthe consequence of a loss of performance, since a certain portion of theraw air inlet has its cross section reduced by the sieve structure. Itwas therefore attempted to increase the mesh width of the sieve.However, this enables flying snow to penetrate and the disadvantagesdescribed above occur, such as the clogging of the filter insert.

Of course, it is also possible to make the raw air inlet cross sectionlarger. Even this entails disadvantages, including among other things,the result that more intake air noise is generated.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to provide an air filter foran internal combustion engine, which will assure optimum separation ofsnow and also will not reduce the cross-sectional area of the raw airinlet to any substantial extent, if at all.

This object is achieved.

The advantage of the invention is that the sieve closing the raw airinlet or the closed flap opens or closes depending on the raw airtemperature. The performance of the movement can be controlled, forexample, by a wax thermostat. Thus, at a temperature above a certainvalue, the full cross section of the raw air opening remains available.The internal combustion engine can develop its maximum power. Below thetemperature limit, i.e., for example at a temperature of less than +2°C., the sieve or the flap closes the raw air inlet and thus preventsentry of snow.

In accordance with one embodiment of the invention, the additional rawair inlet is provided with a weight-loaded or spring-loaded flap. Theclosing force is established such that the valve opens only at a vacuumwhich is formed when the sieve is clogged with snow or the flap hasclosed due to the temperature of the raw air opening.

An additional embodiment of the invention provides for arranging theadditional raw air inlet in the area of a snow-free zone of the motorcompartment. For example, this can be in back of the air cooler. It isalso possible to arrange this raw air inlet near the exhaust manifold,in order thereby to take in heated air.

In order to open the raw air inlet provided with the sieve or the flap,different actuating means can be provided. It is possible to sense thevacuum in the raw air part of the air filter and generate a controlsignal which activates an actuator in accordance with the sensed vacuum.It is also possible to provide a simple expansion thermostat which at acertain temperature turns the sieve or the flap to the appropriateposition. Additional possibilities for turning the sieve or flap aremagnetic drivers or electric drivers.

These and additional features of preferred embodiments of the inventionwill be found not only in the claims but also in the description and thedrawings, the individual features being applicable individually orseverally in the form of subcombinations in the embodiment of theinvention and in other fields and may represent advantageous as well asindependently patentable embodiments, for which protection is herebyclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in further detail below with referenceto working embodiments.

FIG. 1 shows an air filter with an anti-snow system,

FIG. 2 shows a variant of an air filter,

FIG. 3 shows a diagram of the volumetric flow of the intake air suppliedto an internal combustion engine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An air filter according to FIG. 1 has an air filter housing 10. In thishousing an air filter insert 11 is arranged, which is comprised, forexample, of a pleated filter paper which is provided with acircumferential gasket 12 and is arranged with the gasket in areceptacle of the filter housing 10. The filter insert 11 separates aclean air space 13 from a raw air space 14. The clean air space 13 isprovided with a connecting nipple 15. Through this connecting nipple 15the cleaned air flows to an internal combustion engine, not illustratedhere. Within the raw air space 14 is a first intake tube 16 throughwhich the cold air is supplied to the filter system. The intake tube 16is provided at its open end facing the raw air space with a basket sieve17. This basket sieve 17 has a sieve with a mesh width established byexperiment, and serves to effectively entrap snow and ice crystals. Ifthis basket sieve is impinged upon by a large amount of snow, it isunavoidably closed. The intake of air through this intake tube 16 istherefore no longer possible. Intake is impossible also if the pivotablesieve basket is constructed by means of a closed flap.

Therefore an additional intake tube 18 is provided. The inlet of thisintake tube is arranged at a location within a vehicle's motorcompartment that is snow-free. This can be, for example, near theexhaust manifold or directly in back of the radiator housing, but if itis in back of the radiator housing care must be taken that this inletsurface is at right angles to the radiator surface or that its mouth isbehind the motor in the direction of travel.

This additional intake tube is closed by a flap valve 19 at its inneropening facing the raw air space. The flap 19 can either bespring-loaded or alternatively weight-loaded. In the drawing, this valveis configured as a weight-loaded flap and is mounted on a hinge 21 so itcan piviot. In the case of a spring-loaded flap, the spring is locatedin the hinge 21.

As soon as the basket sieve 17 is clogged by snow or snow crystals orthe flap is closed due to the outside air temperature, a vacuum isproduced by the running internal combustion engine in the clean air sideof the intake manifold, which carries over to the raw air side or rawair chamber 14. This vacuum causes the flap 19 to open, so thatcombustion air can flow in through the additional intake tube 18. To theextent that this combustion air is heated, this heating produces thethawing of the snow collected in the basket sieve and thus frees theintake tube 16, so that then fresh air can again be drawn in through theintake tube 16. Thus the vacuum in the raw air space decreases and theflap 19 closes again. The weight of the flap, or the spring force in thecase of a spring-loaded flap, is selected such that the vacuum that isnecessary for the opening of the flap does not increase beyond a certainallowable level.

If the temperature of the aspirated raw air rises above a level at whichthe penetration of snow is unlikely, i.e., at 4° C., for example, a waxthermostat 22 opens the basket sieve 17 or the flap. The basket sieve 17or the flap is attached by a hinge 23 to the intake tube 16. Thus,beginning at this temperature limit the full cross section is availablefor the passage of the intake air or raw air, so that no losses ofperformance of the internal combustion engine need be feared. Only at atemperature below the temperature limit does the wax thermostat 22 closethe intake tube with the basket sieve 17 or the flap and thuseffectively prevents the entry of snow.

FIG. 2 shows a variant of an air filter with an anti-snow system. Hereonly the air intake tract 24 of an air filter for an internal combustionengine is illustrated. In this intake tract there is a mesh plate 25 orflap which also can be operated by a wax thermostat 22. Below atemperature limit of 2° C., for example, the mesh plate 25 or the valveis in the illustrated position, which means that if snow enters throughthe opening 26, it is trapped by the mesh plate 25. At the same time anopening 18′, i.e., the additional intake tube, is opened so thatsnow-free air can flow in.

If the intake temperature exceeds the limit, then the mesh plate ismoved by the wax thermostat to the position indicated by broken linesand closes the additional intake tube 18 and opens up the full crosssection for the raw air.

FIG. 3 shows the different volumetric flows which establish themselvesespecially in a device according to FIG. 1. Volumetric flow V1′ is theraw air flow through the intake tube 16 in the case of a flap valve, andvolumetric flow V1 in the case of a basket sieve 17. Above a temperaturelimit of 2° C., the full cross-sectional area V1′ is available; belowthis temperature limit, the basket sieve or the flap closes the intaketube 16 and thus reduces the maximum volumetric flow. Simultaneously,however, in case of an increase of the vacuum in the raw air space 14 ofthe air filter, the flap valve 19 opens so that an additional volumetricflow V2 can flow into the raw air space.

The internal combustion engine thus has sufficient intake air availablein every operating condition, so that both at higher temperatures andalso at lower temperatures it can achieve its maximum power.

What is claimed is:
 1. An air filter for an internal combustion engine,said filter comprising a housing, a filter insert arranged in thehousing, a clean-air outlet opening out from said housing, and a raw airinlet opening into said housing, a snow blocking element associated withsaid raw air inlet which prevents snow from passing through said inletinto the filter housing, an auxiliary air inlet opening into saidhousing, wherein the snow blocking element is movable between an openposition in which the raw air inlet is unblocked and a blocking positionin which snow is blocked from passing through said raw air inlet;wherein said snow blocking member is moved between said open positionand said blocking position depending on the temperature of raw air drawninto the filter housing, and wherein said snow blocking element is ascreen or sieve having a mesh width small enough to prevent passage ofsnow therethrough.
 2. An air filter according to claim 1, wherein saidsnow blocking element is a flap valve which closes the raw air inlet. 3.An air filter according to claim 1, further comprising a flap valvewhich closes the auxiliary air inlet.
 4. An air filter according toclaim 3, wherein the flap valve which closes the auxiliary air inlet isspring-loaded to a closed position.
 5. An air filter according to claim3, wherein the flap valve which closes the auxiliary air inlet isweight-loaded to a closed position.
 6. An air filter according to claim1, wherein said auxiliary air inlet opens from a snow-free zone of amotor compartment.
 7. An air filter according to claim 1, wherein saidsnow blocking element is moved by an expansion-material thermostat. 8.An air filter according to claim 7, wherein said thermostat is a waxthermostat.
 9. An air filter according to claim 1, wherein said snowblocking element in the open position, blocks said auxiliary air inlet.10. An air filter for an internal combustion engine, said filtercomprising a housing, a filter insert arranged in the housing, aclean-air outlet opening out from said housing, and a raw air inletopening into said housing, a snow blocking element associated with saidraw air inlet which prevents snow from passing through said inlet intothe filter housing, an auxiliary air inlet opening into said housing,wherein the snow blocking element is movable between an open position inwhich the raw air inlet is unblocked and a blocking position in whichsnow is blocked from passing through said raw air inlet; wherein saidsnow blocking member is moved between said open position and saidblocking position depending on the temperature of raw air drawn into thefilter housing, and wherein said snow blocking element is moved by anelectrically or magnetically operated actuator.